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How to Plant and Grow Oyster Leaf (Mertensia maritima)

Oyster (Mertensia maritima)
Photo Credit
David Havel/Shutterstock
Botanical Name
Mertensia maritima
Plant Type
Herbs
Perennial Flowers
Sun Exposure
Part Sun
Soil pH
Slightly Acidic to Neutral
Neutral to Slightly Alkaline
Bloom Time
Summer
Flower Color
Blue
Pink
Hardiness Zone
3
4
5
6
7
Special Features
Attracts Pollinators

Seaside Flavor, No Shucking Shellfish, and A Surprisingly Easy-to-Grow Perennial Herb

Written By: Lauren Landers Master Gardener and Contributing Writer

If you’re looking for a real pearl of a plant, look no further than the oyster leaf. This shell-tactular edible herb has a slightly salty taste that’s reminiscent of an oyster, but growing it is much easier than shucking shellfish—and it’s vegan-friendly. Here’s the scoop on how I grow oyster leaf, planting tips to help it thrive, and how to harvest and use this old-timey plant in seafood dishes and more!

About Oyster Leaf Plants

Also known as the oyster plant, sea bluebells, sea lungwort, and gromwell, oyster leaf (Mertensia maritima) is closely related to borage, and it’s just as versatile! With its distinct bluish-green leaves and nodding, bell-shaped flowers that shift from pink to blue as they mature, oyster leaf has plenty of ornamental appeal. But its leaves and flowers are also edible, and the plant grows perennially in most areas, which means you can enjoy this heirloom herb for many seasons to come.

I like to grow oyster leaf directly in my veggie beds near other lesser-known edibles – like salsify and cardoons – for a vegetable garden that has a bit of an Old World feel. But this plant can also be grown in cottage gardens or other ornamental beds, and its summer-blooming flowers attract pollinators. 

Once mature, you can expect oyster leaf to grow to about 20 inches tall, and it can survive drought, strong winds, and most plant diseases once its roots are established. Not only is oyster leaf ultra cold-tolerant, but it can grow in sandy and gravely soil with low fertility, and it’s impressively salt-tolerant too.

In the wild, oyster leaf grows throughout the Northern Hemisphere and is commonly found along gravelly coastlines near the high tide mark, where the plant is nourished by decaying seaweed. But oyster leaf can also be grown in gardens or in pots and harvested regularly, even if you give it minimal attention!

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Planting

Edible blue leaves of oyster plant
Image credit: COULANGES/Shutterstock

Oyster leaf is a relatively hard-to-find plant. You’re unlikely to spot potted oyster leaf plants at garden centers. If you’re having a hard time tracking down oyster leaf seeds, check out heirloom and traditional seed companies. That’s where I usually find them! I always grow these herbs from seed using the following planting steps.

When to Plant Oyster Leaf

Oyster leaf grows wild in cold climates; its seeds typically sprout better with cold stratification. I’ll usually start cold stratifying oyster leaf seeds in my fridge in early winter, and then plant the stratified seeds in pots in mid-spring. However, oyster leaf seeds can also be cold stratified in the garden by planting the seeds directly in veggie beds or under cold frames when the ground freezes.

How To Plant Oyster Leaf

From Seed (Indoor)

Surface sow oyster leaf seeds in pots filled with damp seed starting mix, and make sure that you don’t bury the seeds under soil. Keep the seeds in bright light, water often, thin out the extra seedlings when they sprout true leaves, and transplant the seedlings into your garden when the risk of spring frost is over. When transplanting, plant oyster leaf seeds to the same depth they were growing in their nursery pots, and space multiple plants at least one foot apart.

From Seed (Outdoor)

Prepare your planting space before the ground freezes by raking away leaves and adding compost if needed. Then, surface sow oyster leaf seeds when the ground is frozen and start watering the seeds when they sprout in spring.

Growing

Oyster Leaf Herb
Image Credit: Joe Kuis/Shutterstock

Once they start growing, oyster leaf plants don’t need much attention, but you can prompt them to grow bushier by pinching back some of their leaves to a leaf node. I like to mulch oyster leaf with pea gravel to imitate its natural growing conditions, but you can mulch these plants with straw or bark mulch, too. 

If your soil is poorly draining, mix some sand and compost in before planting to recreate oyster leaf’s natural growing conditions and improve soil fertility.

Care

Oyster leaf is a perennial herb that should survive winters in cold climates without any winter protection. That said, mulching around your plant’s roots won’t hurt. These plants don’t like hot summers, though, and will need more frequent watering during hot, dry spells.

Throughout the season, I’ll cut damaged or dead oyster leaf stems down to the soil line as they occur, but I rarely do any other pruning. These plants typically flower from June to October and can be used to fill in the bloom gap between spring and fall flowering plants.

For optimal growth, oyster leaf should be fed approximately once a month in spring and summer with a diluted and balanced liquid organic fertilizer. I like to feed these plants with diluted kelp or fish emulsion, but you can use whatever fertilizer you prefer! Oyster leaf doesn’t have any special watering requirements and, like many other edible plants, should be watered when the top one inch of soil feels dry.

Cold-hardy oyster leaf doesn’t mind chilly weather, and a period of cold temperatures can actually help seeds germinate faster. 

Although oyster leaf can grow in full sun locations, these plants prefer areas that receive some light shade in the afternoon.

Harvesting

Oyster Leaf on Pieces of Bread
Image credit: sylv1rob1/Shutterstock

You can harvest oyster leaf plants from June through September, once the plants are at least six inches tall. Just pinch the outer leaves off your plants and pick a few flowers if you’d like to. Be sure to work in batches, though, and never harvest more than 1/3 of your plant’s leaves in one go. Overharvesting can cause oyster leaf plants to stop growing.

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Pests/Diseases

Hardy and resilient, oyster leaf is unbothered by most plant pests and diseases. However, there is one notable exception!

  • Slugs and snails will sometimes trouble oyster leaf plants! They can easily be kept at bay by hand-picking them off the plants and into a bucket of soapy water after heavy rain. You can also create DIY slug traps or “slug pubs” by sinking a cup filled with old beer or orange juice into the soil near oyster leaf plants! 

Propagation

Most gardeners propagate oyster leaf plants from seeds, which can be collected from the plants when the flowers drop their petals in the fall:

  1. Wait for the oyster leaf petals to dry up, and then pluck off the dried seed capsules before they drop their seeds.
  2. Bring the seed capsules indoors and allow them to dry on a screen or plate for a week or two.
  3. Split the capsules open, collect the seeds, and store them in a labeled and dated paper envelope until you plant them!

Wit and Wisdom

  • Oyster leaf can be used in salads, tacos, seafood dishes, and vegan sushi, and can reduce pressure on the seafood industry by offering an eco-friendly alternative to shellfish.
  • When crushed, oyster leaf is said to smell a bit like mushrooms and derives its unique scent from the compound Dimethyl sulfide, which is also found in raw oysters. 

Herbs
About The Author
Lauren Landers

Lauren Landers

Master Gardener and Contributing Writer

Lauren is a gardener, writer, and public speaker with over a decade of experience helping others learn about gardening, homesteading, and sustainable living.She combines years of practical gardening a...
Read More from Lauren Landers

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